Effect of high-temperature plastic deformation on the properties of precipitation-hardening magnesium alloys

Abstract

1. Heating the Mg-3% Nd alloy to a temperature guaranteeing a solid solution of alloying elements in magnesium and high-temperature plastic deformation (80% strain) produce higher strength characteristics at a testing temperature of 250°C than those resulting from treatment T6 (quenching+aging) but lower than those resulting from treatment T8 (quenching +10% cold plastic deformation + aging). 2. At room temperature the strength characteristics of the Mg-3% Nd alloy resulting from high-temperature plastic deformation at 260 and 300 °C are higher than those resulting from treatment T6 or T8. The specific elongation in this case is the same as after treatment T8. High-temperature deformation at 350 °C leads to higher strength properties at room temperature than those resulting from T6 but lower than those from T8. The specific elongation is the same as that resulting from T6. 3. Heating the MA5 alloy to a temperature guaranteeing a solid solution of the alloying elements in magnesium and high-temperature plastic deformation (80% strain) do not increase the strength properties by comparison with the ordinary treatment: hot extrusion without previous heating to guarantee a solid solution and treatment T5 (aging after hot extrusion). 4. The differing effects of high-temperature plastic deformation on the two alloys are reflected in their structures. The structure of Mg-3% Nd alloy is characterized by elongated deformed grains with serrated boundaries. The MA5 alloy is characterized by equi-axed grains, indicating the lack of any substantial distortion of the crystal lattice.